Ventilation unit using temperature and atmospheric pressure equilibrium and preservation system using same

ABSTRACT

An atmospheric pressure equilibrium ventilation unit.

TECHNICAL FIELD

The present invention relates to a ventilation unit using temperature and atmospheric pressure equilibrium and a preservation system using same. More particularly, the present invention pertains to an atmospheric pressure equilibrium ventilation unit for controlling the temperature of an adjacent place using the hot energy or cold energy generated from one heating device or cooling device and a preservation system using same.

BACKGROUND ART

In a household refrigerator, the temperature of a refrigerating room can be adjusted by one evaporator of a freezing room without installing an additional evaporator in the refrigerating room. However, in a large-scale industrial or commercial work-in cooler or freezing refrigerator, the size of a fan of a freezing room evaporator and the size of a damper and a duct interconnecting the freezing room and the refrigerating room become larger. Thus, there is a problem in that an air is difficult to smoothly circulate due to the heat loss, the ice formation in the damper and the atmospheric pressure rise in the refrigerator and the atmospheric pressure drop in the freezer generated when blowing the air existing in the freezer to the refrigerator.

Furthermore, a heat loss is generated in the freezer due to the introduction of an external air into the freezer through an atmospheric pressure valve which is installed to remove a negative pressure attributable to a temperature drop in the freezer. A heat loss is induced because the air existing in the refrigerator having an increased atmospheric pressure is discharged to the outside through an atmospheric pressure valve installed in the refrigerator. This poses a problem in that the material cost, the labor cost and the power consumption are increased. Despite the increase in the costs, freezers are respectively installed in individual refrigerators in the case where the capacity of a freezing refrigerator is high. Even when a single condensing unit is used, individual coolers are installed in a freezer and a refrigerator. A cooling medium pipe is connected to the freezer.

Even in the case a plurality of freezing rooms and a plurality of refrigerating rooms are employed, freezers are installed in the respective rooms. At least indoor units are installed in the respective rooms and a cooling medium pipe is connected to a condensing unit.

SUMMARY OF THE INVENTION Technical Problems

It is an object of the present invention to provide an atmospheric pressure equilibrium ventilation unit capable of rapidly and accurately supplying an air exiting in a storeroom to an adjacent storeroom and capable of maintaining pressure equilibrium between the storerooms adjoining each other.

Another object of the present invention is to provide a preservation system using the atmospheric pressure equilibrium ventilation unit mentioned above.

A further object of the present invention is to solve a problem that a heat loss is generated in a freezer due to the introduction of an external air into the freezer through an atmospheric pressure valve which is installed to remove a negative pressure attributable to a temperature drop in the freezer and further that a heat loss is largely induced because an air existing in a refrigerator having an increased atmospheric pressure is discharged to the outside through an atmospheric pressure valve installed in the refrigerator.

However, the problems to be solved by the present invention are not limited to the aforementioned ones but may be differently expanded without departing from the spirit and scope of the present invention.

Means for Solving the Problems

In order to achieve the above objects, an atmospheric pressure equilibrium ventilation unit according to an exemplary embodiment, includes:

a first frame assembly including a first frame configured to define a first ventilation hole, a first rotation shaft installed in the first ventilation hole, and a first opening/closing plate provided in the first rotation shaft and configured to rotate together with the first rotation shaft to open and close the first ventilation hole;

a second frame assembly disposed adjacent to the first frame assembly, the second frame assembly including a second frame configured to define a second ventilation hole, a second rotation shaft installed in the second ventilation hole and a second opening/closing plate provided in the second rotation shaft and configured to rotate together with the second rotation shaft to open and close the second ventilation hole, the second opening/closing plate configured to open and close the second ventilation hole by being rotated by a difference between atmospheric pressures applied to opposite sides of the second opening/closing plate;

a drive unit connected to the first rotation shaft, the drive unit including a reversible motor configured to rotate the first rotation shaft in a forward direction or a reverse direction in response to an opening signal or a closing signal;

a drive control unit connected to the first rotation shaft and the reversible motor and configured to control the reversible motor by cutting off the opening signal or the closing signal when the first rotation shaft is rotated by a predetermined angle; and

a locking control unit connected to the first rotation shaft and the second rotation shaft and configured to lock the second rotation shaft to keep the second ventilation hole in a closed state when the first rotation shaft is rotated by a predetermined angle in response to the opening signal to open the first ventilation hole.

In an exemplary embodiment, the first ventilation hole may include a first lower ventilation hole and a first upper ventilation hole disposed in a vertical direction, the first rotation shaft including a first lower rotation shaft installed in the first lower ventilation hole and a first upper rotation shaft installed in the first upper ventilation hole, the first opening/closing plate including a first lower opening/closing plate provided in the first lower rotation shaft and a first upper opening/closing plate provided in the first upper rotation shaft.

In an exemplary embodiment, the first upper rotation shaft may be connected to a first link, the first lower rotation shaft may be connected to a second link, and the first link and the second link may be interconnected by a connection link.

In an exemplary embodiment, the first link may be an input link connected to a drive shaft of the reversible motor, and the second link may be an output link.

Alternatively, the second link may be an input link connected to a drive shaft of the reversible motor, and the first link may be an output link.

In an exemplary embodiment, the locking control unit may include:

an balancing blade formed in at least one end portion of the second rotation shaft and provided with a locking protrusion portion protruding in a horizontal direction; and

a fixing blade connected to the connection link and configured to move upward, make contact with the locking protrusion portion and hold the balancing blade against movement when the first rotation shaft is rotated by a predetermined angle in response to the opening signal.

In an exemplary embodiment, the locking protrusion portion may include at least two locking protrusion portions spaced apart from each other in the horizontal direction, and when the first rotation shaft is rotated, the fixing blade may be configured to move upward, make contact with the two locking protrusion portions and horizontally fix the balancing blade.

In an exemplary embodiment, the first frame may include a dividing frame configured to divide the first lower ventilation hole and the first upper ventilation hole.

In an exemplary embodiment, the dividing frame may become gradually thinner toward one end portion thereof.

In an exemplary embodiment, stopper strips may be formed in a central portion of an inner surface of the first frame and in a central portion of a dividing frame, and the first opening/closing plate may be seated on the stopper strips when the first rotation shaft is rotated by a predetermined angle.

In an exemplary embodiment, protrusion portions may be formed in a central portion of an inner surface of the second frame and in a central portion of a lower surface of the second frame, heater insertion grooves may be provided in the stopper strips and the protrusion portions, and heaters may be fitted to the heater insertion grooves to prevent ice formation in the first and second frames and the first and second opening/closing plates.

In an exemplary embodiment, the drive control unit may include:

a first micro switch operatively connected to the first rotation shaft and configured to cut off the opening signal when the first rotation shaft is rotated by a predetermined angle in response to the opening signal;

a second micro switch operatively connected to the first rotation shaft and configured to cut off the closing signal when the first rotation shaft is rotated by a predetermined angle in response to the closing signal; and

a drive circuit including relays respectively connected to the first and second micro switches and configured to stop the reversible motor when one of the opening signal and the closing signal is cut off.

In an exemplary embodiment, when the first rotation shaft is rotated by 90° in an opening direction, the contact point of the first micro switch may be opened to cut off the opening signal, and when the first rotation shaft is rotated by 90° in a closing direction, the contact point of the second micro switch may be opened to cut off the closing signal.

In an exemplary embodiment, the first link may be configured to rotate by a predetermined angle in an opening direction with respect to the first upper rotation shaft and then to make contact with the first micro switch to cut off the opening signal, and the second link may be configured to rotate by a predetermined angle in a closing direction with respect to the second lower rotation shaft and then to make contact with the second micro switch to cut off the closing signal.

In an exemplary embodiment, the second opening/closing plate may be configured to be opened when a difference is generated between atmospheric pressures applied to opposite sides of the second opening/closing plate and to be closed when the difference between atmospheric pressures is removed, the second rotation shaft may be positioned in an uppermost area of the second ventilation hole, and the second opening/closing plate may have a gravity center which exists lower than the second rotation shaft so that the second opening/closing plate closes the second ventilation hole by an own weight of the second opening/closing plate.

In an exemplary embodiment, the second opening/closing plate may have a recess region disposed in a lower portion thereof and depressed in a concave shape so as to receive an air pressure, and the second opening/closing plate may have a lower end surface which makes contact with a lower horizontal frame, the lower surface formed into a curved surface so as to minimize a frictional resistance between the second opening/closing plate and the lower horizontal frame when opening and closing the second ventilation hole.

In an exemplary embodiment, the second opening/closing plate may be configured to be opened by a difference between atmospheric pressures applied to front and rear sides of the second opening/closing plate and, when the difference between atmospheric pressures is removed, the second opening/closing plate may be returned to a closed position by a restoring force of a return spring provided in one end portion of the second rotation shaft.

In an exemplary embodiment, the second opening/closing plate may be configured to be opened by a difference between atmospheric pressures applied to front and rear sides of the second opening/closing plate, when the difference between atmospheric pressures is removed, the second opening/closing plate may be returned to a closed position by a restoring force of a return spring provided in one end portion of the second rotation shaft, and when the second opening/closing plate comes close to the closed position, the air tightness of the second opening/closing plate may be enhanced by a magnetic force acting between a first magnetic portion provided in a lower end portion of the second opening/closing plate and a second magnetic portion provided in the second frame in a corresponding relationship with the first magnetic portion.

In an exemplary embodiment, the ventilation unit may further include: a temperature controller configured to supply the opening signal and the closing signal to the reversible motor depending on a temperature of a storeroom in which the ventilation unit is installed.

In an exemplary embodiment, the ventilation unit may further include: a ventilation fan disposed on one side surface of the first frame and configured to discharge or supply an air through the first ventilation hole.

In an exemplary embodiment, the ventilation fan may be configured to operate when the opening signal is supplied and to stop when the closing signal is supplied.

In order to achieve the above objects, a preservation system according to an exemplary embodiment, include:

a first storeroom having a heat source;

a second, storeroom disposed adjacent to the first storeroom with a wall interposed between the first storeroom and the second storeroom,

a first atmospheric pressure equilibrium ventilation unit installed in the wall and configured to supply an air existing within the first storeroom to the second storeroom; and

a second atmospheric pressure equilibrium ventilation unit installed in the wall in an adjoining relationship with the first atmospheric pressure equilibrium ventilation unit and configured to supply an air existing within the second storeroom to the first storeroom.

At least one of the first and second atmospheric pressure equilibrium ventilation units may include:

a first frame assembly including a first frame configured to define a first ventilation hole, a first rotation shaft installed in the first ventilation hole, and a first opening/closing plate provided in the first rotation shaft and configured to rotate together with the first rotation shaft to open and close the first ventilation hole;

a second frame assembly disposed adjacent to the first frame assembly, the second frame assembly including a second frame configured to define a second ventilation hole, a second rotation shaft installed in the second ventilation hole and a second opening/closing plate provided in the second rotation shaft and configured to rotate together with the second rotation shaft to open and close the second ventilation hole, the second opening/closing plate configured to open and close the second ventilation hole by being rotated by a difference between atmospheric pressures applied to opposite sides of the second opening/closing plate;

a drive unit connected to the first rotation shaft, the drive unit including a reversible motor configured to rotate the first rotation shaft in a forward direction or a reverse direction in response to an opening signal or a closing signal;

a drive control unit connected to the first rotation shaft and the reversible motor and configured to control the reversible motor by cutting off the opening signal or the closing signal when the first rotation shaft is rotated by a predetermined angle; and

a locking control unit connected to the first rotation shaft and the second rotation shaft and configured to lock the second rotation shaft to keep the second ventilation hole in a closed state when the first rotation shaft is rotated by a predetermined angle in response to the opening signal to open the first ventilation hole.

In an exemplary embodiment, the first storeroom may be a low-temperature storeroom having a low-temperature heat source, the second storeroom may be a heat-receiving low-temperature storeroom which receives a cold air from the first storeroom, and the heat source of the first storeroom may include a freezer.

In an exemplary embodiment, the first storeroom may be a heat source warmer cabinet having a heat source, the second storeroom may be a heat-receiving warmer cabinet, the heat source of the first storeroom may include a heater and a heat pump.

In an exemplary embodiment, the system may further include: a temperature controller configured to supply the opening signal and the closing signal to the reversible motor depending on internal temperatures of the first and second storeroom.

In an exemplary embodiment, at least one of the first and second atmospheric pressure equilibrium ventilation units may further include a ventilation fan disposed on one side surface of the first frame and configured to discharge or supply an air through the first ventilation hole.

In an exemplary embodiment, the ventilation fan may be configured to operate when the opening signal is supplied and to stop when the closing signal is supplied.

In an exemplary embodiment, the second frame of the atmospheric pressure equilibrium ventilation unit may be an atmospheric pressure equilibrium assembly.

In an exemplary embodiment, the system may further include: an external atmospheric pressure equalizer installed in at least one of the first and second storerooms and configured to maintain pressure equilibrium between the inside and outside of the first and second storerooms.

In an exemplary embodiment, the system may further include: an atmospheric pressure valve installed in the second storeroom which receives a cold air and a hot air and configured to maintain pressure equilibrium between the inside and outside of the first and second storerooms.

Effects of the Invention

The atmospheric pressure equilibrium ventilation unit of the present invention configured as above is installed between two or more storerooms having different temperatures (or between a heat source warmer cabinet and a heat-receiving warmer cabinet). When a temperature is to be kept low, an air existing in a low-temperature storeroom having a low-temperature heat source is supplied to an adjoining storeroom whose temperature is to be controlled. When a temperature is to be kept high, an air existing in a high-temperature storeroom having a high-temperature heat source is supplied to an adjoining storeroom whose temperature is to be controlled. At this time, a positive pressure generated in an air-receiving storeroom is returned to an air-supplying storeroom, thereby making up for a negative pressure of the air-supplying storeroom and maintaining atmospheric pressure equilibrium. Thus, the air is smoothly circulated. This makes it possible to control the temperature of an adjoining target storeroom.

For this purpose, a dedicated ventilation unit made of a non-metallic material having a low heat transfer coefficient is employed so as to cut off heat transfer and air leakage. In order to prevent ice formation in a damper, a dedicated heater is installed in a frame body of a ventilation assembly in which a damper plate rotates. A geared motor is used as an opening/closing power source in order to accurately open and close the damper with a strong force. A dedicated drive circuit is employed to operate the damper. An atmospheric pressure difference generated when opening and closing an entrance door and when circulating an air, namely a difference in internal pressure between a first storeroom and a second storeroom may be removed by an atmospheric pressure equilibrium assembly. An atmospheric pressure difference between the storeroom and the outside may be removed by an external atmospheric pressure equalizer.

Furthermore, an external atmospheric pressure equalizer is installed in the second storeroom which is a cold-air-receiving room or a hot-air-receiving room, whereby the pressure of the first and second storerooms is balanced with the pressure of the external air through the second storeroom which has a low temperature difference with the external air. As compared with a case where the pressure of the internal air having a relatively large temperature difference is balanced with the pressure of the external air through the first storeroom, it is possible to prevent a sudden temperature change and a sudden thermal shock otherwise applied to a stored product. It is also possible to save energy.

In the case where heat sources are installed in both the first storeroom and the second storeroom, if one of the first storeroom and the second storeroom is broken down and if products are stored in the broken-down storeroom, the products may be denatured due to an abrupt change in temperature. In most cases, a repairman is pushed for time to repair the broken-down storeroom.

In this case, if the atmospheric pressure equilibrium ventilation unit of the present invention is installed, the heat source of the non-broken-down storeroom may be used to supply heat required in the broken-down storeroom.

In the case of a storeroom capable of controlling a temperature, the facility thereof is installed in view of a maximum load. It is therefore possible to save the time required in repairing a broken-down storeroom. Thus, the facility may serve as a preliminary facility for use in an emergency situation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a preservation system according to an exemplary embodiment.

FIG. 2 is a perspective view of a ventilation assembly of an atmospheric pressure equilibrium ventilation unit according to an exemplary embodiment, which is kept in a closed state.

FIG. 3 is a front view of the ventilation assembly illustrated in FIG. 2.

FIG. 4 is a right side view of the ventilation assembly illustrated in FIG. 2.

FIG. 5 is a left side view of the ventilation assembly illustrated in FIG. 2.

FIG. 6 is a perspective view of the ventilation assembly of the atmospheric pressure equilibrium ventilation unit illustrated in FIG. 2, which is kept in an open state.

FIG. 7 is a front view of the ventilation assembly Illustrated in FIG. 6.

FIG. 8 is a right side view of the ventilation assembly illustrated in FIG. 6.

FIG. 9 is a perspective view of an atmospheric pressure equilibrium assembly of the atmospheric pressure equilibrium ventilation unit illustrated in FIG. 2, which is kept in an open state.

FIG. 10 is a right side view of the atmospheric pressure equilibrium assembly illustrated in FIG. 9.

FIG. 11 is a perspective view of the atmospheric pressure equilibrium assembly of the atmospheric pressure equilibrium ventilation unit illustrated in FIG. 2, which is kept in an open state.

FIG. 12 is a right side view of the atmospheric pressure equilibrium assembly illustrated in FIG. 11.

FIG. 13 is a sectional view illustrating a second opening/closing plate which is kept in a closed state.

FIG. 14 is a sectional view illustrating the second opening/closing plate which is kept in an open state.

FIG. 15 is an exploded perspective view illustrating an atmospheric pressure equilibrium ventilation unit according to an exemplary embodiment.

FIG. 16 is a side view illustrating the atmospheric pressure equilibrium ventilation unit illustrated in FIG. 15.

FIG. 17 is a circuit diagram which employs the atmospheric pressure equilibrium ventilation unit of the preservation system illustrated in FIG. 1.

FIG. 18 is a side view illustrating a balancing blade connected to a single return spring.

FIGS. 19 and 20 are perspective views illustrating first frames for a ventilation assembly having different structures.

FIG. 21 is a perspective view illustrating a preservation system according to an exemplary embodiment.

FIG. 22 is a circuit diagram illustrating an automatic exhaust system of the preservation system illustrated in FIG. 21.

BEST MODE FOR CARRYING OUT THE INVENTION

Specific structural and functional descriptions on the embodiments of the present invention disclosed herein are illustrated merely for the purpose of describing the embodiments of the present invention. The present invention may be carried out in many different forms and shall not be construed to be limited to the embodiments disclosed herein.

The present invention may be differently modified and may have different forms. Specific embodiments will now be illustrated in the drawings and will be described in detail. However, this is not intended to limit the present invention to specific forms disclosed herein. It is to be understood that all the modifications, equivalents and substitutions are included in the spirit and technical scope of the present invention.

Terms “first” and “second” may be used in describing different components. However, the components shall not be limited by the terms. The terms may be used to distinguish one component from another component. For example, a first component may be named as a second component without departing from the protection scope of the present invention. Similarly, a second component may be named as a first component.

When there is a description that one component is “connected” or “coupled” to another component, it is to be understood that one component is connected or coupled to another component either directly or through the intervention of a third component. On the other hand, when there is a description that one component is “directly connected” or “directly coupled” to another component, it is to be understood that a third component does not exist between one component and another component. Other expressions that describe the relationship between components, for example, the expressions “between”, “directly between”, “adjoining” and “directly adjoining” shall be construed in a similar manner.

The terms used herein are used merely for the purpose of describing specific embodiments and are not intended to limit the present invention. A singular expression includes a plural expression unless explicitly mentioned otherwise. In the subject application, it is to be understood that the term “include” or “have” is intended to indicate the existence of a feature, a number, a step, an operation, a component, a part or a combination thereof and is not intended to intentionally exclude the existence or the possibility of addition of one or more features, numbers, steps, operations, components, parts or combinations thereof.

Unless defined otherwise, all the terms used herein, including the technical or scientific terms, have the same meanings as ordinarily understood by a person having an ordinary knowledge in the technical field to which the present invention pertains. The terms ordinarily used and defined in a dictionary shall be interpreted to have the meanings that match with the contextual meanings of the related art. The terms shall not be interpreted in ideal or excessively formal meanings unless explicitly defined otherwise herein.

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Identical components in the drawings will be designated by like reference symbols with duplicate descriptions thereon omitted.

FIG. 1 is a perspective view illustrating a preservation system according to an exemplary embodiment. Referring to FIG. 1, the preservation system 10 may include a first storeroom 12, a second storeroom 14 and first and second atmospheric pressure equilibrium ventilation units 100A and 100B installed between the first storeroom 12 and the second storeroom 14.

In the exemplary embodiment, the preservation system 10 may include at least two first and second storerooms 12 and 14 having mutually-different temperature ranges and adjoining each other. The first storeroom 12 and the second storeroom 14 may be disposed adjacent to each other with an intermediate wall 16 interposed therebetween. The temperature ranges of the first and second storerooms 12 and 14 may be set depending on the kind of stored products which are stored in the respective storerooms.

For example, the first storeroom 12 may be a low-temperature storeroom such as a freezer or the like, which includes a low-temperature heat source 30 such as a cooler or the like. The second storeroom 14 may be a low-temperature storeroom such as a refrigerator having a temperature higher than the temperature of the first storeroom or the like, which receives a cold air from the first storeroom. Alternatively, the first storeroom 12 may be a heat source warmer cabinet having a high-temperature heat source such as a heater or the like. The second storeroom 14 may be a heat-receiving warmer cabinet having a temperature range lower than the temperature of the heat source warmer cabinet.

The first atmospheric pressure equilibrium ventilation unit 100A and the second atmospheric pressure equilibrium ventilation unit 100B may be installed on the same intermediate wall 16 and are apart from each other. The first and second atmospheric pressure equilibrium ventilation units 100A and 100B, which form a pair, are capable of supplying an air existing in the first storeroom 12 to the second storeroom 14 and supplying an air existing in the second storeroom 14 to the first storeroom 12.

The positions of the first and second atmospheric pressure equilibrium ventilation units 100A and 100B may be selected in view of the size and temperature range of the first and second storerooms 12 and 14.

The first atmospheric pressure equilibrium ventilation unit 100A may selectively supply the air existing in the first storeroom 12 to the second storeroom 14. The second atmospheric pressure equilibrium ventilation unit 100B may selectively supply the air existing in the second storeroom 14 to the first storeroom 12. The first and second atmospheric pressure equilibrium ventilation units 100A and 100B may be operated at the same time. For example, when the first atmospheric pressure equilibrium ventilation unit 100A is operated to supply the air existing in the first storeroom 12 to the second storeroom 14, the second atmospheric pressure equilibrium ventilation unit 100B may be simultaneously operated to supply the air existing in the second storeroom 14 to the first storeroom 12. Furthermore, when the air supply operation of the first atmospheric pressure equilibrium ventilation unit 100A is stopped, the air supply operation of the second atmospheric pressure equilibrium ventilation unit 100B may also be stopped.

As will be described later, at least one of the first and second atmospheric pressure equilibrium ventilation units 100A and 100B may include a ventilation assembly which may be selectively opened to supply the air existing in one storeroom to another storeroom and an atmospheric pressure equilibrium assembly for maintaining pressure equilibrium between the storerooms.

The ventilation assembly may open and close a first ventilation hole provided between the first and second storerooms 12 and 14 in response to control signals such as an opening signal and a closing signal. When the first ventilation hole is opened, the ventilation assembly may perform an air supply operation. The atmospheric pressure equilibrium assembly is provided adjacent to the ventilation assembly and may be opened by the atmospheric pressure difference between the first and second storerooms 12 and 14 to remove the atmospheric pressure difference. Furthermore, the atmospheric pressure equilibrium assembly may keep a second ventilation hole in a closed state when the first ventilation hole is opened, thereby cutting off the flow of an air through the atmospheric pressure equilibrium assembly.

In the exemplary embodiment, the preservation system 10 may further include a sensor unit (not illustrated). The sensor unit may include a gas sensor, a pressure sensor, a humidity sensor, a temperature sensor and the like, which are installed within the first storeroom 12 and the second storeroom 14. The sensor unit is connected to a control unit (not illustrated). The control unit may control the operation of the preservation system 10 depending on the temperature, humidity and gas concentration within the storerooms, which are detected by the sensor unit. For example, the control unit includes temperature controllers 50A and SOB. Depending on the internal temperature of the first and second storerooms 12 and 14, the temperature controllers 50A and 50B may generate and supply control signals for controlling the air supply operations of the first and second atmospheric pressure equilibrium ventilation units 100A and 100B.

Furthermore, the preservation system 10 may further include an external atmospheric pressure equalizer 40 installed in at least one of the first and second storerooms 12 and 14 to maintain pressure equilibrium between the inside and outside of the first and second storerooms 12 and 14. For example, the external atmospheric pressure equalizer 40 may be installed in one sidewall of the second storeroom 14 and may be opened when an atmospheric pressure difference exists between the inside and outside of the second storeroom 14, thereby removing the atmospheric pressure difference.

Hereinafter, the atmospheric pressure equilibrium ventilation unit included in the preservation system illustrated in FIG. 1 will be described in detail.

For the sake of clear understanding, the first atmospheric pressure equilibrium ventilation unit 100A and the second atmospheric pressure equilibrium ventilation unit 100B illustrated in FIG. 1 are opposite to each other in the air supply and discharge directions and may include identical or similar components. For example, in the case where the first storeroom is a freezer and the second storeroom is a refrigerator, the first and second atmospheric pressure equilibrium ventilation units 100A and 100B may include ventilation fans disposed at the side of the second storeroom 14 in order to prevent ice formation in the first and second opening/closing plates and the ventilation fans. In the case where the first storeroom is a heat source warmer cabinet and the second storeroom is a heat-receiving warmer cabinet, the first and second atmospheric pressure equilibrium ventilation units 100A and 100B may include ventilation fans disposed at the side of the second storeroom 14 in order to prevent the overheating of the ventilation fans.

Hereinafter, the first and second atmospheric pressure equilibrium ventilation units 100A and 100B will be designated by reference symbol 100 and will be generally referred to as an atmospheric pressure equilibrium ventilation unit.

FIG. 2 is a perspective view of the ventilation assembly of the atmospheric pressure equilibrium ventilation unit according to the exemplary embodiment, which is kept in a closed state. FIG. 3 is a front view of the ventilation assembly illustrated in FIG. 2. FIG. 4 is a right side view of the ventilation assembly illustrated in FIG. 2. FIG. 5 is a left side view of the ventilation assembly illustrated in FIG. 2. FIG. 6 is a perspective view of the ventilation assembly of the atmospheric pressure equilibrium ventilation unit illustrated in FIG. 2, which is kept in an open state. FIG. 7 is a front view of the ventilation assembly illustrated in FIG. 6. FIG. 8 is a right side view of the ventilation assembly illustrated in FIG. 6. FIG. 9 is a perspective view of the atmospheric pressure equilibrium assembly of the atmospheric pressure equilibrium ventilation unit illustrated in FIG. 2, which is kept in an open state. FIG. 10 is a right side view of the atmospheric pressure equilibrium assembly illustrated in FIG. 9. FIG. 11 is a perspective view of the atmospheric pressure equilibrium assembly of the atmospheric pressure equilibrium ventilation unit illustrated in FIG. 2, which is kept in an open state. FIG. 12 is a right side view of the atmospheric pressure equilibrium assembly illustrated in FIG. 11. FIG. 13 is a sectional view illustrating the second opening/closing plate which is kept in a closed state. FIG. 14 is a sectional view illustrating the second opening/closing plate which is kept in an open state. FIG. 15 is an exploded perspective view illustrating the atmospheric pressure equilibrium ventilation unit according to the exemplary embodiment. FIG. 16 is a side view illustrating the atmospheric pressure equilibrium ventilation unit illustrated in FIG. 15. FIG. 17 is a circuit diagram which employs the atmospheric pressure equilibrium ventilation unit of the preservation system illustrated in FIG. 1.

Referring to FIGS. 2 to 17, the atmospheric pressure equilibrium ventilation unit 100 according to the exemplary embodiment may include a ventilation assembly, an atmospheric pressure equilibrium assembly and a ventilation fan unit 200. The ventilation fan unit 200 may be installed at one side of the ventilation assembly. The ventilation fan unit 200 may include a ventilation fan 202 for discharging and supplying an air existing in one storeroom to another storeroom through the ventilation assembly 110.

The ventilation assembly may include a first frame assembly installed in the wall 16 existing between the first and second storerooms 12 and 14 and provided with first ventilation holes 116 a and 116 b, a drive unit 140 configured to open and close the first ventilation holes 116 a and 116 b in response to control signals such as an opening signal and a closing signal, and a drive control unit configured to control the drive unit 140. The ventilation assembly may discharge or supply an air through the first ventilation holes 116 a and 116 b by operating the ventilation fan 202 with the first ventilation holes 116 a and 116 b kept opened.

The atmospheric pressure equilibrium assembly may include a second frame assembly installed in the wall 16 in the vicinity of the first frame assembly of the ventilation assembly and provided with a second ventilation hole 126 which may be opened by the atmospheric pressure difference between the first and second storerooms 12 and 14 to remove the atmospheric pressure difference, and a locking control unit which is operatively connected to the ventilation assembly and configured to keep the second ventilation hole 126 in a closed stat so that the second ventilation hole 126 is not opened when the first ventilation holes 116 a and 116 b are opened.

In the exemplary embodiment, the atmospheric pressure equilibrium ventilation unit 100 is divided into a multi-story type and a stacked type, the operation principle of which is identical or similar. The multi-story type will be first described here.

Referring to FIGS. 2 to 11, the first frame assembly may include a first frame 110 installed in the wall existing between the first and second storerooms and configured to define the first ventilation holes 116 a and 116 b, first rotation shafts 114 a and 114 b installed in the first ventilation holes 116 a and 116 b, and first opening/closing plates 117 a and 117 b provided in the first rotation shafts 114 a and 114 b and configured to rotate together with the first rotation shafts 114 a and 114 b to open and close the first ventilation holes 116 a and 116 b.

The first frame 110 may include first vertical frames 111 a and 111 b and first horizontal frames 112 a and 112 b for defining at least one of the first ventilation holes 116 a and 116 b opened. For example, the first frame 110 may include an first upper ventilation hole 116 a and a first lower ventilation hole 116 b which are disposed along the vertical direction. The first frame 110 may include a dividing frame 113 which defines the first upper ventilation hole 116 a and the first lower ventilation hole 116 b. The first upper ventilation hole 116 a and the first lower ventilation hole 116 b divided by the dividing frame 113 are disposed one above another along the vertical direction, thereby providing a multi-story ventilation assembly. Alternatively, as will be described later, it may be possible to provide a staked type ventilation assembly (see FIGS. 19 and 20) in which a plurality of first frames 110 is stacked in the vertical direction and the horizontal direction.

The first upper ventilation hole 116 a may be identical in shape with the first lower ventilation hole 116 b. For example, the first upper and lower ventilation holes 116 a and 116 b may have a tetragonal cross-sectional shape. The first ventilation holes may have a rectangular cross-sectional shape with the width thereof being larger than the height thereof. Thus, the first frame 110 having a tetragonal window may include at least two first ventilation holes 116 a and 116 b divided by at least one dividing frame 113 extending across the center of the first frame 110.

There may be provided two or more dividing frames. In this case, three or more first ventilation holes may be provided depending on the number of the dividing frames. Alternatively, as will be described later, only one first ventilation hole may be provided in the first frame 110. In this case, a plurality of first frames may be combined and disposed in the left-right direction or the up-down direction, thereby providing a stacked ventilation assembly (see FIGS. 19 and 20) having a plurality of first ventilation holes.

The first upper and lower rotation shafts 114 a and 114 b may be respectively installed in the first upper and lower ventilation holes 116 a and 116 b. The first upper rotation shaft 114 a is installed to extend cross the first upper ventilation hole 116 a. At least one end portion of the first upper rotation shaft 114 a may protrude outward from the first frame 110. The first lower rotation shaft 114 b is installed to extend cross the first lower ventilation hole 116 b. At least one end portion of the first lower rotation shaft 114 b may protrude outward from the first frame 110.

The first upper and lower opening/closing plates 117 a and 117 b may be respectively coupled to the first upper and lower rotation shafts 114 a and 114 b. The first upper opening/closing plate 117 a may have a reception hole into which the first upper rotation shaft 114 a is inserted and fixed. The first lower opening/closing plate 117 b may have a reception hole into which the first lower rotation shaft 114 b is inserted and fixed. Thus, the first upper and lower rotation shafts 114 a and 114 b may be respectively inserted and fixed into the reception holes of the first upper and lower opening/closing plates 117 a and 117 b.

The first upper opening/closing plate 117 a is installed in the first upper rotation shaft 114 a and may open or close the first upper ventilation hole 116 a as the first upper rotation shaft 114 a rotates in a forward or reverse direction. The first lower opening/closing plate 117 b is installed in the first lower rotation shaft 114 b and may open or close the first lower ventilation hole 116 b as the first lower rotation shaft 114 b rotates in a forward or reverse direction.

Alternatively, the first opening/closing plates may be fitted to slits formed in the first rotation shafts and may be coupled to the first rotation shafts by the combination of bolts and nuts or the combination of bolts and taps formed in the first rotation shafts. The first opening/closing plates may be integrally formed with the first rotation shafts.

In the exemplary embodiment, first and second stopper strips 118 a, 118 b, 119 a and 119 b may be respectively formed on the inner surfaces of the first frame 110 and the dividing frame 113.

More specifically, the first stopper strip 118 a is formed to protrude from the inner surfaces of the first vertical frames 111 a and 111 b and the lower surface of the first horizontal frame 112 a. The second stopper strip 119 a is formed to protrude from the inner surfaces of the first vertical frames 111 a and 111 b and the upper surface of the dividing frame 113. When the first opening/closing plate 117 a is in a position in which the first opening/closing plate 117 a completely closes the first ventilation hole 116 a, the end portions of the first opening/closing plate 117 a make contact with the first and second stopper strips 118 a and 119 a.

Furthermore, the first stopper strip 118 b is formed to protrude from the inner surfaces of the first vertical frames 111 a and 111 b and the lower surface of the dividing frame 113. The second stopper strip 119 b is formed to protrude from the inner surfaces of the first vertical frames 111 a and 111 b and the upper surface of the first horizontal frame 112 b. When the first opening/closing plate 117 b is in a position in which the first opening/closing plate 117 b completely closes the first ventilation hole 116 b, the end portions of the first opening/closing plate 117 b make contact with the first and second stopper strips 118 b and 119 b. This makes it possible to improve the air tightness of the first opening/closing plates 117 a and 117 b and the first ventilation holes 116 a and 116 b.

Furthermore, heater insertion grooves 218 a, 218 b, 219 a and 219 b are respectively provided in the first and second stopper strips 118 a, 118 b, 119 a and 119 b. Heaters are inserted into the respective heater insertion grooves. The heaters may prevent the first opening/closing plates 117 a and 117 b from being frozen and seized by the first frame 110 at a low temperature.

As illustrated in FIGS. 15 and 16, the drive unit 140 is provided on the side surface of the first frame 110 and may include a reversible motor 142 for rotating the first rotation shafts in a forward direction or a reverse direction. The reversible motor 142 may be mounted to the side surface of the first frame 110 by a motor bracket 143.

The drive unit 140 may further include a speed reducer 144 connected to a drive shaft of the reversible motor 142. The speed reducer 144 may include a gear train connected to the drive shaft of the reversible motor 142 and may stably maintain the operations of the first rotation shafts and the first opening/closing plates. Thus, the reversible motor 142 of the drive unit 140 may serve as a geared motor which rotates at a low speed and obtains a large torque.

The drive shaft of the reversible motor 142 may be connected to one of the first upper and lower rotation shafts 114 a and 114 b. Specifically, the drive shaft of the reversible motor 142 may be connected to one end portion of the first upper rotation shaft 114 a via a coupling 145 and may rotate the first upper rotation shaft 114 a in a forward direction or a reverse direction.

The first upper rotation shaft 114 a is connected to a first link 150 and the first lower rotation shaft 114 b is connected to a second link 152. The first link 150 and the second link 152 may be interconnected by a connection link 154. Thus, the first upper rotation shaft 114 a and the first lower rotation shaft 114 b may form a four-joint link in cooperation with the aforementioned links. In this case, the length of the first link 150 may be equal to the length of the second link 152. When the drive shaft of the reversible motor 142 is directly connected to the first upper rotation shaft 114 a protruding from the first frame 110, the first link 150 may be an input link and the second link 152 may be an output link. Alternatively, the second link 152 may be an input link and the first link 150 may be an output link. Thus, if the first upper rotation shaft 114 a is rotated by the reversible motor 142, the first lower rotation shaft 114 b may rotate in the same direction as the rotation direction of the first upper rotation shaft 114 a.

In the exemplary embodiment, the first upper rotation shaft and the first lower rotation shaft may be interconnected through a connection means such as a gear train, a cam mechanism, a timing belt or the like. The drive shaft of the reversible motor may be connected to the first upper rotation shaft by a sleeve, a coupling, a speed reducing gear and a joint and may rotate the first upper rotation shaft in a forward direction or a reverse direction.

Furthermore, power sources such as reversible motors or solenoids may be respectively connected to the first upper rotation shaft and the first lower rotation shaft. These power sources may simultaneously perform an opening/closing operation in response to a single signal.

Alternatively, only one of the opening/closing plates may be operated in response to an individual signal. The circuit for detecting and controlling the opening level of the opening/closing plates may control the opening degree and opening angle of the opening/closing plates and may control the supply amount and flow direction of an air by virtue of proportional control rather than on/off detection and control.

The reversible motor 142 is connected to and controlled by a temperature controller 50. The reversible motor 142 may rotate in a forward direction or a reverse direction in response to a control signal such as an opening signal or a closing signal.

As illustrated in FIGS. 2 to 12, if the reversible motor 142 rotates in the forward direction in response to the opening signal, the first upper and lower rotation shafts 114 a and 114 b may rotate in an opening direction and may open the first upper and lower ventilation holes 116 a and 116 b. If the reversible motor 142 rotates in the reverse direction in response to the closing signal, the first upper and lower rotation shafts 114 a and 114 b may rotate in a closing direction and may close the first upper and lower ventilation holes 116 a and 116 b.

In the exemplary embodiment, the drive control unit is connected to the first rotation shafts 114 a and 114 b and the reversible motor 142. If the first rotation shafts 114 a and 114 b are rotated by a predetermined angle, the drive control unit may cut off the opening signal or the closing signal to stop the reversible motor 142. The drive control unit may include a first micro switch 160, a second micro switch 162 and a drive circuit.

The first and second micro switches 160 and 162 are operatively connected to the first upper and lower rotation shafts 114 a and 114 b and may change the flow of an electrical signal pursuant to the mechanical movement (e.g., the rotational movement) of the first upper and lower rotation shafts 114 a and 114 b.

More specifically, the first micro switch 160 is operatively connected to the first upper rotation shaft 114 a and may cut off the opening signal when the first upper rotation shaft 114 a is rotated by a predetermined angle in response to the opening signal. The second micro switch 162 is operatively connected to the first lower rotation shaft 114 b and may cut off the closing signal when the first lower rotation shaft 114 b is rotated by a predetermined angle in response to the closing signal.

The first micro switch and the second micro switch may be proximity sensors or other sensors capable of recognizing an operation. A circuit for improving the operation stability may be formed by installing both the micro switches and the proximity sensors.

As illustrated in FIGS. 4 and 8, the first link 150 and the first upper rotation shaft 114 a may rotate by a predetermined angle (e.g., 90°) in response to the opening signal. Thereafter, the other end portion of the first link 150 may make contact with the first micro switch 160. Thus, the contact point of the first micro switch 160 may be opened to cut off the supply of the opening signal to the reversible motor 142.

The second link 152 and the first lower rotation shaft 114 b may rotate by a predetermined angle (e.g., 90°) in response to the closing signal. Thereafter, the other end portion of the second link 152 may make contact with the second micro switch 162. Thus, the contact point of the second micro switch 162 may be opened to cut off the supply of the closing signal to the reversible motor 142.

Thus, when the first rotation shafts 114 a and 114 b are rotated by 90° in the opening direction, the contact point of the first micro switch 160 may be opened to cut off the opening signal. When the first rotation shafts 114 a and 114 b are rotated by 90° in the closing direction, the contact point of the second micro switch 162 may be opened to cut off the closing signal.

As illustrated in FIGS. 1 and 17, the temperature controller 50 may supply the opening signal and the closing signal to the reversible motor 142 depending on the temperatures measured by temperature sensors 50 a and 50 b installed within the first and second storerooms. The drive circuit interconnects the temperature controller 50 and the reversible motor 142. The drive circuit may include relays respectively connected to the first and second micro switches 160 and 162 and configured to stop the reversible motor 142 if one of the opening signal and the closing signal is cut off.

In the exemplary embodiment, if the internal temperature of the second storeroom falls outside a predetermined temperature range, the contact point T/C of the temperature controller 50 is closed and electric power may be supplied to both the ventilation fan and the relay AX1 via a B-contact point DTb2 of a defrosting timer of a first storeroom controller.

If a cold air is supplied to the second storeroom when the freezer of the first storeroom is under a defrosting process, there is a possibility that the internal temperature of the first storeroom increases. Thus, the cold air is not supplied to the second storeroom during the defrosting time but is supplied to the second storeroom after the defrosting is completed.

Furthermore, DC power of 12 V may be supplied from a DC power supply device SMPS to a DC relay DAX1 via a B-contact point of a first micro switch S/W1 and an A-contact point AX1-1 a of a relay AX1.

If a ventilation opening relay DAX1 is energized, DC power of 12 V is applied to a reversible ventilation motor M/A via A-contact points DAX1-1 a and DAX1-2 a of the ventilation opening relay DAX1. Thus, the first link 150 may be operated in the direction in which the first opening/closing plates 117 of the ventilation unit are opened. The second link 152 and the fixing blade 157, which are operatively connected to the first link 150, may move upward.

While moving upward, the fixing blade 157 may horizontally restrain a balancing blade 130 provided in a rotation shaft of a second opening/closing plate 125. If the second opening/closing plate 125 is rotated by an angle of 90°, a protruding head of a bolt interconnecting the first link 150 and the fixing blade 157 makes contact with the lever of the first micro switch 160. Thus, the contact point of the first micro switch 160 may be opened to cut off the DC power supplied to the ventilation opening relay DAX1.

The reversible motor 142 is stopped in a state in which the electric power supplied to the reversible motor M/A of the ventilation unit is cut off and the first opening/closing plates 117 are rotated by 90° and opened. The ventilation fan 202 ventilates the air existing in the first storeroom and the second storeroom in a state in which the first ventilation holes 116 are opened. The ventilation fan 202 may operate until the internal temperature of the second storeroom reaches a temperature set by the temperature controller T/C.

If the internal temperature of the second storeroom falls within a predetermined temperature range, the contact point of the temperature controller 50 (T/C) is opened to cut off the electric power supplied to the ventilation fan and the relay AX1. Thus, the ventilation fan may be stopped.

Thus, the b-contact point AX1-2 b of the relay AX1 is closed and the reversible motor 142 DAX2 is rotated in the reverse direction via the b-contact point of the first micro switch and the contact point AX1-2 b, thereby rotating the first upper rotation shaft 114 a in the closing direction. The second link 152 operatively connected to the first link 150 is also rotated in the closing direction to rotate the first lower rotation shaft 114 b in the closing direction. This makes it possible to close the first upper and lower ventilation holes 116 a and 116 b.

If the first upper rotation shaft 114 a is rotated by a predetermined angle (e.g., 90°) in the closing direction, the second link 152 is also rotated so that the other end portion of the second link 152 may make contact with the second micro switch 162. As a result, the contact point of the second micro switch 162 is opened to cut off the electric power supplied to the relay DAX2. Thus, the contact points DAX2-1 a and DAX2-2 a are opened to cut off the supply of the closing signal to the reversible motor 142, whereby the reverse rotation of the reversible motor 142 may be stopped. At this time, the first upper and lower ventilation holes 116 a and 116 b may be completely closed.

The reason for supplying the electric power to the ventilation fan and the relay AX1 via the B-contact point Dtb2 of the defrosting timer of the first storeroom controller is as follows. If a cold air is supplied to the second storeroom when the freezer of the first storeroom is under a defrosting process, there is a fear that the internal temperature of the first storeroom increases. Thus, the cold air is not supplied to the second storeroom during the defrosting time but is supplied to the second storeroom after the defrosting is completed.

As described above, in order for the drive control unit to compensate the operation of the first and second micro switches and to protect the reversible motor 142, it may be possible to serially connect proximity sensors to the micro switches. Thus, even if the micro switches are not operated, the proximity sensors may cut off the electric power supplied to the reversible motor 142 and may safely protect the reversible motor 142.

In this regard, the reason for forming the control circuit as a DC circuit is to secure the safety and to reduce the size of the drive motor.

As illustrated in FIGS. 2 to 14, the atmospheric pressure equilibrium ventilation unit may include a second frame 120 installed in the wall between the first and second storerooms adjoining each other and configured to define a second ventilation hole 126, a second rotation shaft 124 installed in the second ventilation hole 126, and a second opening/closing plate 125 provided in the second rotation shaft 124 and configured to rotate together with the second rotation shaft 124 to open or close the second ventilation hole 126.

The second frame 120 may be disposed above the first frame 110. For example, the second frame 120 may be stacked on the first frame 110. Alternatively, the second frame 120 may be integrally formed with the first frame 110. The second frame 120 may include second vertical frames 121 a and 121 b and a second horizontal frame 122 a for defining at least one second ventilation hole 126. Thus, the second ventilation hole 126 may be defined by the second vertical frames 121 a and 121 b, the second horizontal frame 122 a and the first horizontal frame 112 a. The second ventilation hole 126 may have a tetragonal cross-sectional shape. The second ventilation hole may have a rectangular cross-sectional shape with the width thereof being larger than the height. The second ventilation hole 126 may be smaller in width and height than the first ventilation holes 116 a and 116 b.

The second rotation shaft 124 may be installed in the second ventilation hole 126. The second rotation shaft 124 is installed to extend across the second ventilation hole 126. The opposite end portions of the second rotation shaft 124 may protrude outward through the through-holes of the second frame 120. Within the second ventilation hole 126, the second opening/closing plate 125 may be coupled to the second rotation shaft 124. The second opening/closing plate 125 may be installed in the second rotation shaft 124 so as to rotate in both directions with respect to the second rotation shaft 124. The second opening/closing plate 125 may be rotated in both directions with respect to the second rotation shaft 124, thereby opening or closing the second ventilation hole 126.

For example, the second opening/closing plate 125 may have a reception hole into which the second rotation shaft 124 is inserted and fixed. Thus, the second rotation shaft 124 may be inserted and fixed into the reception hole of the second opening/closing plate 125. Furthermore, the second rotation shaft 124 may be disposed to extend across the uppermost area of the second ventilation hole 126. The second opening/closing plate 125 may be provided so as to extend only in one direction from the second rotation shaft 124. The second opening/closing plate 125 may be fitted to the second rotation shaft 124 extending across the uppermost area of the second frame 120 and may be fixed to the second rotation shaft 124 by a fixing means such as a bolt or the like. Alternatively, the second opening/closing plate may be integrally formed with the second rotation shaft.

Furthermore, the second rotation shaft 124 may be supported by oilless bearings installed in the through-holes of the second frame 120 and may serve as an atmospheric pressure valve which is smoothly rotated by the differential pressure of an air.

In the exemplary embodiment, equilibrium blades 130 are provided in the opposite end portions of the second rotation shaft 124 protruding from the second frame 120. First and second return springs 132 a and 132 b may be connected to the opposite end portions of each of the equilibrium blades 130. One end portions of the first and second return springs 132 a and 132 b may be fixed to the outer portion of the second frame 120. The first and second return springs 132 a and 132 b may be connected to the opposite end portions of each of the equilibrium blades 130 in a V-like shape.

If a difference between the pressures applied to the front and rear sides of the second opening/closing plate is larger than the biasing force of the first and second return springs 132 a and 132 b, the second rotation shaft 124 and the second opening/closing plate 125 are rotated in one direction to open the second ventilation hole 126. At this time, if the first return spring 132 a receives a tensile force due to the rotation of the balancing blade 130, the second return spring 132 b may receive a compression force. Conversely, if the second return spring 132 b receives a compression force, the second return spring 132 b may receive a tensile force.

If the difference between the pressures applied to the front and rear sides of the second opening/closing plate is removed, the balancing blade 130 is returned to the horizontal state by the restoring force of the first and second return springs 132 a and 132 b. Thus, the second opening/closing plate 125 may return to the original position and may close the second ventilation hole 126.

First and second protrusion portions 123 and 128 may be formed on the inner surface of the second frame 120. When the second opening/closing plate 125 is in the vertical position (the closing position), the opposite side portions of the second opening/closing plate 125 are positioned adjacent to the first protrusion portion 123, and the lower end portion of the second opening/closing plate 125 is positioned adjacent to the second protrusion portion 128, thereby maintaining the air tightness in the second ventilation hole 126.

Unlike the first stopper strips 118 a and 118 b of the first frame 110, the first protrusion portion 123 of the second frame 120 may be formed to protrude from the opposite side surfaces of the second frame 120 (the inner surfaces of the second vertical frames 121 a and 121 b) so that, when the second opening/closing plate 125 performs the opening/closing operation using the atmospheric pressure difference, the opposite side portions of the second opening/closing plate 125 may move while touching the first protrusion portion 123.

As illustrated in FIGS. 13 and 14, unlike the second stopper strips 119 a and 119 b of the first frame 110, the second protrusion portion 128 of the second frame 120 may be formed to protrude from the lower surface of the second frame 120 (the upper surface of the first horizontal frame 112 a) so that the lower end portion of the second opening/closing plate 125 may move while touching the second protrusion portion 128. This makes it possible to improve the air tightness between the second opening/closing plate 125 and the second ventilation hole 126 while not restricting the opening/closing operation of the second opening/closing plate 125.

Furthermore, a heater insertion groove is formed in the first protrusion portion 123. A heater H is inserted into the heater insertion groove and the second protrusion portion 128. The heater H may prevent the second opening/closing plate 125 from being frozen and seized to the second frame 120 at a low temperature. The heater H may be sealed and fixed by a sealing member S such as an epoxy molding compound or the like.

Furthermore, the second opening/closing plate 125 may further include a semicircular weight portion 125 b which is provided in the lower end portion of the second opening/closing plate 125 in order to increase the force of restoration to the vertical position by the gravity center. The weight portion 125 b of the second opening/closing plate 125 may include a first magnetic portion M1 and the second protrusion portion 128 may include a second magnetic portion M2 corresponding to the first magnetic portion M1.

Accordingly, when the second opening/closing plate 125 is opened and then closed again, the air tightness of the second ventilation hole 126 may be enhanced by the restoring force of the first and second return springs 132 a and 132 b connected to the balancing blade 130 and by the magnetic force of the first and second magnetic portions M1 and M2.

The atmospheric pressure equilibrium assembly is operatively connected to the ventilation assembly so that the atmospheric pressure equilibrium assembly is closed when the ventilation assembly is opened. This makes it possible to maintain the second ventilation hole 126 in a closed state when the first ventilation holes 116 a and 116 b are opened. More specifically, the locking control unit is connected to the first rotation shafts 114 a and 114 b and the second rotation shaft 124. When the first rotation shafts 114 a and 114 b are rotated by a predetermined angle in response to the opening signal to open the first ventilation holes 116 a and 116 b, the locking control unit may lock the second rotation shaft 124 to keep the second ventilation hole 126 in a closed state.

In the exemplary embodiment, the locking control unit may include a locking protrusion portion 131 formed in the balancing blade 130 so as to protrude in the horizontal direction, and a locking fixing portion operatively connected to the first rotation shafts 114 a and 114 b and configured to make contact with the locking protrusion portion 131 and inhibit the rotational movement of the balancing blade 130 when the first ventilation holes 116 a and 116 b are opened.

The balancing blade 130 may be formed in one end portion of the second rotation shaft 124. Two locking protrusion portions 131 may be formed to horizontally protrude outward from the balancing blade 130. The two locking protrusion portions 131 may be horizontally spaced apart from each other when the second opening/closing plate 125 is in a vertical state (a closed state). In addition, the locking protrusion portion 131 may have a contact surface oriented in the vertical direction.

The locking fixing portion may include a fixing blade 157 which extends in a direction orthogonal to an extension arm 156 extending upward from one end portion of the connection link 154. The extension arm 156 is operatively connected to the first rotation shafts 114 a and 114 b and is moved upward when the first rotation shafts 114 a and 114 b rotate a predetermined angle (e.g., 90°) in response to the opening signal. As the extension arm 156 is moved upward, the fixing blade 157 is also moved upward to make contact with the locking protrusion portions 131, thereby inhibiting the rotational movement of the balancing blade 130.

As shown in FIGS. 4 and 8, when the first rotation shafts 114 a and 114 b rotate by a predetermined angle in response to the opening signal, the extension arm 156 is moved upward toward the balancing blade 130. The fixing blade 157 makes contact with the contact surfaces of the locking protrusion portions 131 and pushes up the balancing blade 130 in a horizontal state, thereby fixing the balancing blade 130 against movement.

That is to say, if the first link 150 rotates by a predetermined angle (e.g., 90°) in response to the opening signal, the connection link 154 is moved upward. The fixing blade 157 connected to the extension arm 156 in an inverted L-like shape horizontally pushes up the balancing blade 130, thereby fixing the second rotation shaft 124 against movement. As a result, when the first ventilation holes 116 a and 116 h are in an open state, the second ventilation hole 126 comes into a closed state and may not serve as an atmospheric pressure valve.

On the contrary, when the first rotation shafts 114 a and 114 b rotate by a predetermined angle in response to the closing signal, the extension arm 156 is moved downward and the fixing blade 157 is moved away from the locking protrusion portions 131 of the balancing blade 130. Thus the restraint of the balancing blade 130 is released and the second rotation shaft 124 may rotate along with the rotation of the second opening/closing plate 125.

That is to say, if the second link 152 rotates by a predetermined angle (e.g., 90°) in response to the closing signal, the connection link 154 is moved downward and the fixing blade 157 is moved away from the balancing blade 130, whereby the restraint of the second rotation shaft 124 may be released. Therefore, when the first ventilation holes 116 a and 116 b are in a closed state, the second ventilation hole 126 may serve as an atmospheric pressure valve capable of removing an atmospheric pressure difference.

FIG. 18 is a side view illustrating a balancing blade connected to a single return spring. Referring to FIG. 18, the return spring 132 may be connected to the lower central portion of the balancing blade 130. In this case, if the second rotation shaft 124 is rotated by an atmospheric pressure difference, the return spring 132 may receive a tensile force. If the atmospheric pressure difference is removed, the balancing blade 130 may be returned to the horizontal position by the restoring force of the return spring 132.

FIGS. 19 and 20 are perspective views illustrating first frames for a ventilation assembly having different structures.

Referring to FIG. 19, the first frame assembly of the ventilation assembly may include first frames 110 a and 110 b disposed side by side. Each of the first frames 110 a and 110 b may define a plurality of first ventilation holes.

Referring to FIG. 20, the first frame assembly of the ventilation assembly may include first frames 110 a and 110 b vertically stacked one above another.

Hereinafter, descriptions will be made on the operations of the atmospheric pressure equilibrium ventilation units of the freezing/refrigerating system according to the exemplary embodiments.

First, descriptions will be made on the operations of the first and second atmospheric pressure equilibrium ventilation units 100A and 100B in the preservation system 10 in which the first storeroom 12 of FIG. 1 is a heat source storeroom having a low temperature and the second storeroom 14 is a storeroom having a relatively high temperature.

If the first atmospheric pressure equilibrium ventilation unit 100A supplies the cold air of the first storeroom 12 having a low temperature to the second storeroom 14 having a relatively high temperature, the temperature of the second storeroom 14 goes down and the atmospheric pressure goes up. At the same time, the second atmospheric pressure equilibrium ventilation unit 100B blows the air existing within the second storeroom 14 toward the first storeroom 12 having a low temperature. Thus, the air existing within the second storeroom 14 circulates toward the first storeroom 12 having a low temperature. As a result, the temperature of the first storeroom 12 goes up and the temperature of the second storeroom 14 goes down.

If the temperature of the first storeroom 12 goes up and reaches a predetermined cut-in temperature (e.g., −18° C.), the cooling medium is supplied to the evaporator by the temperature controller which controls the internal temperature of the first storeroom 12. The evaporator fan and the compressor are operated to cool the air having a relatively high temperature, which is supplied from the second storeroom 14. Thus, the temperature of the first storeroom 12 is reduced.

On the other hand, if the air temperature is reduced by the cold air supplied from the first storeroom 12 and if the temperature of the second storeroom 14 reaches a predetermined temperature (e.g., 0° C.), the first and second atmospheric pressure equilibrium ventilation units allow the first opening/closing plates 117 a and 117 b to rotate about the first rotation shafts 114 a and 114 b, thereby closing the first ventilation holes 116 a and 116 b which are air circulation paths. Then, the first and second atmospheric pressure equilibrium ventilation units stop the ventilation fans 202.

If the supply of the cold air to the second storeroom 14 is stopped, the internal temperature of the first storeroom 12 rapidly goes down and reaches a predetermined cut-off temperature (e.g., −20° C.). The electromagnetic valve installed in a liquid line through which a cooling medium is supplied to a freezer evaporator 30 is closed by the temperature controller which controls the internal temperature of the first storeroom 12. Thus, the supply of the cooling medium is stopped. The operations of an evaporator fan and a compressor are stopped.

Thereafter, if the temperature of the second storeroom 14 is increased again by the products stored within the second storeroom 14 and the heat infiltrated from the outside and if the temperature of the second storeroom 14 reaches a predetermined cut-in temperature (e.g., 2° C.), the reversible motor 142 is rotated in the forward direction by the temperature controller which controls the internal temperature of the second storeroom 14. Thus, the first opening/closing plates 117 a and 117 b of the first and second atmospheric pressure equilibrium ventilation units 100A and 100B are rotated to open the first ventilation holes 116 a and 116 b. Then, the ventilation fans 202 are operated. The ventilation fans 202 draw the cold air existing in the first storeroom 12 and blow the air existing in the second storeroom 14 toward the first storeroom 12. By virtue of the circulation of the air, the temperature of the second storeroom 14 is decreased again. If the temperature of the second storeroom 14 goes down and reaches a predetermined cut-off temperature (e.g., 0° C.), the reversible motor 142 is rotated in the reverse direction by the temperature controller which controls the internal temperature of the second storeroom 14. Thus, the first opening/closing plates 117 a and 117 b are rotated to close the first ventilation holes 116 a and 116 b. The ventilation fans 202 are kept stopped until the temperature of the second storeroom 14 reaches a predetermined cut-in temperature (e.g., 2° C.).

On the other hand, if the temperature of the first storeroom 12 goes up and reaches a predetermined cut-in temperature (e.g., −18° C.), the liquid line electromagnetic valve is opened by the temperature controller which controls the internal temperature of the first storeroom 12. Thus, the cooling medium is supplied to the evaporator. The evaporator fan and the compressor are operated again.

If the temperature of the first storeroom 12 goes down and reaches a predetermined cut-off temperature (e.g., −20° C.), the liquid line electromagnetic valve is closed by the temperature controller which controls the internal temperature of the first storeroom 12. Thus, the supply of the cooling medium to the evaporator is stopped. The ventilation fans 202 are kept stopped until the temperature of the first storeroom 12 reaches a predetermined cut-in temperature (e.g., −18° C.).

On the other hand, if the air temperature and atmospheric pressure within the first storeroom 12 are decreased by the cold air generated from the evaporator 30, the atmospheric pressure equilibrium assembly of the atmospheric pressure equilibrium ventilation unit serves as an atmospheric pressure valve. Thus, the air existing within the second storeroom 14 moves toward the first storeroom 12 through the second ventilation hole 126 kept opened. This makes it possible to maintain the equilibrium of the atmospheric pressure. When the internal pressure of the first storeroom 12 is instantaneously increased by closing a heat insulation door of the first storeroom 12 and when the internal pressure of the second storeroom 14 is instantaneously increased by closing a heat insulation door of the second storeroom 14, the atmospheric pressure equilibrium ventilation unit maintains the pressure equilibrium by bypassing the high-pressure air existing between the first storeroom 12 and the second storeroom 14 through the second ventilation hole 126. Under the control of the temperature controller 50, the atmospheric pressure equilibrium ventilation unit circulates the air. This makes it possible to control the required temperature between the first storeroom 12 and the second storeroom 14.

In the meantime, when the first ventilation holes 116 a and 116 b of the ventilation assembly are opened, the fixing blade 157 connected to the upper end of the extension arm 156 restrains movement of the balancing blade 130 of the second rotation shaft, whereby the second opening/closing plate 125 which opens and closes the second ventilation hole 126 is kept in a closed position. The second opening/closing plate 125 is freely moved only when the first ventilation holes 116 a and 116 b of the ventilation assembly are closed.

Owing to this structure, it is possible to prevent the following problem. Specifically, a negative pressure may be locally generated around the ventilation unit of the first storeroom 12 during the operation of the ventilation fan of the atmospheric pressure equilibrium ventilation unit. In this case, the second ventilation hole 126 as an atmospheric pressure valve is opened so that the air drawn from the first storeroom is returned to the first storeroom. Similarly, the air drawn from the second storeroom is returned to the second storeroom. As a result, the air existing within the first storeroom and the second storeroom does not circulate through the first storeroom and the second storeroom as a whole but circulate through only a local area.

Next, descriptions will be made on the operations of the first and second atmospheric pressure equilibrium ventilation units 100A and 100B within the preservation system 10 in which the first storeroom 12 is a heat source warmer cabinet and the second storeroom 14 is a heat-receiving warmer cabinet.

If the first atmospheric pressure equilibrium ventilation unit 100A supplies the hot air existing within the high-temperature heat source warmer cabinet 12 to the heat-receiving warmer cabinet 14, the temperature and atmospheric pressure of the heat-receiving warmer cabinet 14 are increased. At the same time, if the second atmospheric pressure equilibrium ventilation unit 100B supplies the hot air existing within the heat-receiving warmer cabinet 14 to the heat source warmer cabinet 12, the air existing within the heat-receiving warmer cabinet 14 is circulated toward the heat source warmer cabinet 12. Thus, the temperature of the heat source warmer cabinet 12 is decreased and the temperature of the heat-receiving warmer cabinet 14 is increased. If the temperature of the heat source warmer cabinet 12 goes down and reaches a predetermined cut-in temperature (e.g., 45° C.), electric power is supplied to the heater 30 as a heat source by the temperature controller which controls the internal temperature of the heat source warmer cabinet 12. Thus, the heater and the fan are operated within the heat source warmer cabinet 12, thereby increasing the temperature of the heat source warmer cabinet 12.

If the temperature of the heat-receiving warmer cabinet 14 is increased to a predetermined cut-off temperature (e.g., 50° C.) by the hot air supplied from the heat source warmer cabinet 12, the atmospheric pressure equilibrium ventilation unit allows the first opening/closing plates 117 a and 117 b to rotate about the first rotation shafts 114 a and 114 b, thereby closing the first ventilation holes 116 a and 116 b which are air circulation paths. Then, the ventilation fan 202 is stopped.

If the supply of the hot air to the heat-receiving warmer cabinet 14 is sopped, the internal temperature of the heat source warmer cabinet 12 is rapidly increased to a predetermined cut-off temperature (e.g., 60° C.). The electric power supplied to the heater 30 is cut off by the temperature controller which controls the internal temperature of the heat source warmer cabinet 12. The operations of the fan and the heater are stopped.

Thereafter, if the temperature of the heat-receiving warmer cabinet 14 is decreased again to a predetermined cut-in temperature (e.g., 45° C.) by the heat absorbed to the products stored within the heat-receiving warmer cabinet 14 and the heat leaked to the outside, the reversible motor 142 is rotated in the forward direction by the temperature controller which controls the internal temperature of the heat-receiving warmer cabinet 14. Thus, the first opening/closing plates 117 a and 117 b of the first and second atmospheric pressure equilibrium ventilation units 100A and 100B are rotated to open the first ventilation holes 116 a and 116 b. Then, the ventilation fans 202 are operated. The ventilation fans 202 draw the hot air from the heat source warmer cabinet 12 and blow the air existing in the heat-receiving warmer cabinet 14 toward the heat source warmer cabinet 12. By virtue of this circulation of the air, the temperature of the heat-receiving warmer cabinet 14 is increased again.

If the temperature of the heat-receiving warmer cabinet 14 is increased to a predetermined cut-off temperature (e.g., 50° C.), the reversible motor 142 is rotated in the reverse direction by the temperature controller which controls the internal temperature of the heat-receiving warmer cabinet 14. Thus, the first opening/closing plates 117 a and 117 b are rotated to close the first ventilation holes 116 a and 116 b. Then, the ventilation fans 202 are kept stopped until the temperature of the heat-receiving warmer cabinet 14 reaches a predetermined cut-in temperature (e.g., 45° C.).

On the other hand, if the temperature of the heat source warmer cabinet 12 is decreased to a predetermined cut-in temperature (e.g., 55° C.), electric power is supplied to the heater by the temperature controller 50 which controls the internal temperature of the heat source warmer cabinet 12. The fan 202 of the heat source warmer cabinet 12 is operated again.

If the temperature of the heat source warmer cabinet 12 is increased to a predetermined cut-off temperature (e.g., 60° C.), the electric power supplied to the heater and the fan of the heat source warmer cabinet 12 is cut off by the temperature controller which controls the internal temperature of the heat source warmer cabinet 12. The operation of the heat source warmer cabinet 12 is stopped until the temperature of the heat source warmer cabinet 12 reaches a predetermined cut-in temperature (e.g., 55° C.).

On the other hand, if the air temperature and atmospheric pressure within the heat source warmer cabinet 12 are increased by the hot air generated from the heater 30, the atmospheric pressure equilibrium assembly of the atmospheric pressure equilibrium ventilation unit serves as an atmospheric pressure valve. Thus, the air existing within the heat source warmer cabinet 12 moves toward the heat-receiving warmer cabinet 14 through the second ventilation hole 126 kept opened. This makes it possible to maintain the equilibrium of the atmospheric pressure.

When the internal pressure of the heat source warmer cabinet 12 is instantaneously increased by closing a heat insulation door of the heat source warmer cabinet 12, the atmospheric pressure equilibrium ventilation unit maintains the pressure equilibrium by bypassing the air through the second ventilation hole 126. This makes it possible to control the internal temperature of the warmer cabinets by circulating the air between the heat source warmer cabinet 12 and the heat-receiving warmer cabinet 14.

In the meantime, even when a pressure unbalance is generated between the first storeroom and the second storeroom and the second ventilation hole is opened so that the air existing in the first storeroom is moved to the second storeroom or the air existing in the second storeroom to the first storeroom, the time during which the second ventilation hole is opened by the difference in atmospheric pressure is extremely short. Thus, the preservation system may be controlled within a predetermined temperature range.

In the case where heat sources are installed in both the first storeroom and the second storeroom, if one of the first storeroom and the second storeroom is broken down and if products are stored in the broken-down storeroom, the products may be denatured due to an abrupt change in temperature. In most cases, a repairman is pushed for time to repair the broken-down storeroom.

In this case, if the atmospheric pressure equilibrium ventilation unit of the present invention is installed, the heat source of the non-broken-down storeroom may be used to supply heat required in the broken-down storeroom.

In the case of a storeroom capable of controlling a temperature, the facility thereof is installed in view of a maximum load. It is therefore possible to save the time required in repairing a broken-down storeroom. Thus, the facility may serve as a preliminary facility for use in an emergency situation.

FIG. 21 is a perspective view illustrating a preservation system according to an exemplary embodiment. FIG. 22 is a circuit diagram illustrating an automatic exhaust system of the preservation system illustrated in FIG. 21. This preservation system is substantially identical with the preservation system illustrated in FIG. 1, except that the atmospheric pressure equilibrium ventilation unit does not include an atmospheric pressure equilibrium assembly and further that the atmospheric pressure equilibrium ventilation unit is installed in the wall of one storeroom. The same components will be designated by like reference symbols with duplicate descriptions thereof omitted.

Referring to FIGS. 21 and 22, the atmospheric pressure equilibrium ventilation unit according to an exemplary embodiment is an improvement of the exhaust unit disclosed in Korean Patent No. 10-0933006. In this exemplary embodiment, only a first storeroom exists. A first ventilation unit for drawing an external air into the first storeroom (or the first room) may be installed in a wall of the first storeroom (or the first room). A second ventilation unit for discharging the gas existing within the first storeroom (or the first room) may be installed in another wall not affected by the first ventilation unit. Agricultural products or other products may exist within the first storeroom (or the first room). If there is a possibility that the concentration of a harmful gas generated from the products stored within the first storeroom (or the first room) or a harmful gas introduced from the outside is equal to or higher than a predetermined concentration and may be harmful to a person, the concentration of the harmful gas is detected and the harmful gas is automatically discharged to the outside using the ventilation unit. The fresh external air is drawn into the first storeroom to maintain the internal gas concentration at a predetermined value or less.

More specifically, there may be provided a system in which if the gas detected within the first storeroom is a gas generated by fire, the air existing within the first storeroom is discharged to the outside and the fresh external air is supplied into the first storeroom and in which if the gas detected within the first storeroom is a specific toxic gas other than the gas generated by fire, the toxic gas is discharged to the outside and an oxygen gas or a pre-prepared gas capable of neutralizing the toxic gas is supply into the first storeroom.

As described above, the atmospheric pressure equilibrium ventilation unit according to the present invention is installed between two or more low-temperature storerooms having different temperatures or between a freezer and a refrigerator (or between a heat source warmer cabinet and a heat-receiving warmer cabinet) so that the cold air existing within a storeroom having a heat source and having a relatively low temperature is supplied to an adjoining storeroom whose temperature is to be kept low. Thus, the temperature of the adjoining storeroom may be controlled without having to install an additional freezer in the adjoining storeroom. This system may be realized not only between a freezer and a refrigerator but also between a freezer and a freezer and between a refrigerator and a refrigerator. The system is capable of controlling a temperature as long as a small temperature difference may be generated between a storeroom having a cold energy source and a cold-energy-receiving storeroom having no cold energy source. Thus, the system is widely applicable in the industry.

Furthermore, the air of a heat source warmer cabinet having a relatively high temperature may be supplied to a heat-receiving warmer cabinet in which a temperature is to be kept high. Thus, the temperature of the adjoining heat-receiving warmer cabinet may be controlled without having to install an additional heat source in the adjoining heat-receiving warmer cabinet. This makes it possible to control the temperatures of different adjoining storerooms through the use of a single heat source.

Even in the conventional industrial or commercial freezing/refrigerating storerooms, there is used a method of controlling a temperature by using a single condensing unit and installing respective coolers in two or more places having different temperatures. However, in this method, a cooler need to be installed in a refrigerating room. As a result, it is necessary to install facilities such as a cooling medium pipe, a defrosting water pipe, a complex electric wiring line and the like. Furthermore, an expensive evaporation pressure control valve need to be installed in a cooling medium pipe in order to solve a problem which may be caused by a pressure drop in a cooling medium pipe of a refrigerating room attributable to an evaporation temperature difference.

Furthermore, a variety of problems is generated due to the installation and operation of a cooler. For example, there are many problems such as a rapid increase in a room temperature during a defrosting time, an installation constraint in a narrow space due to the necessity of an additional space corresponding to the length of a heater required in replacing a defrosting heater in a cooler installation process, and the necessity of frequent repair attributable to damage of a defrosting heater.

However, according to the present invention, a small-sized atmospheric pressure equilibrium ventilation unit for lowering the temperature of a refrigerating room is installed in a partition wall. This eliminates the need to install a cooling medium pipe, a defrosting water pipe, a cooler and an evaporation pressure control valve. This provides various advantages such as the saving of mechanical equipment, the ease of installation, the saving of labor costs, the reduction use amount of the cooling medium, the utilization of a cooler installation space due to the non-installation of a cooler, the needlessness of securing a cooler installation space and a defrosting heater replacement space, and so forth.

In the meantime, the capacity of a freezer installed in a freezing room need to be the total sum of the capacity of a freezing room and the capacity of a refrigerating room. If a freezer is installed only in a freezing room, as compared with a case where freezers are installed in both a freezing room and a refrigerating room, there are provided many advantages such as the saving of a material cost, a labor cost, an installation cost and a maintenance cost, the increase in a usable space, and the like.

In the case where heat sources are installed in both a first storeroom and a second storeroom, the heat source of one of the first storeroom and the second storeroom (e.g., the heat source of the second storeroom) may be broken down and products may be stored within the storeroom whose heat source is broken down. In this case, if there is installed the atmospheric pressure equilibrium ventilation unit of the present invention, the non-broken-down heat source of one of the storeroom (e.g., the first storeroom) may make up for the broken-down heat source. This makes it possible to save the time required in repairing the broken-down heat source. Thus, the facility may serve as a preliminary facility for use in an emergency situation.

While exemplary embodiments of the present invention have been described above, it will be understood by a person skilled in the art that the present invention may be changed and modified in many different forms without departing from the spirit and scope of the present invention defined in the appended claims. 

1. An atmospheric pressure equilibrium ventilation unit, comprising: a first frame assembly including a first frame configured to define a first ventilation hole, a first rotation shaft installed in the first ventilation hole, and a first opening/closing plate provided in the first rotation shaft and configured to rotate together with the first rotation shaft to open and close the first ventilation hole; a second frame assembly disposed adjacent to the first frame assembly, the second frame assembly including a second frame configured to define a second ventilation hole, a second rotation shaft installed in the second ventilation hole and a second opening/closing plate provided in the second rotation shaft and configured to rotate together with the second rotation shaft to open and close the second ventilation hole, the second opening/closing plate configured to open the second ventilation hole by being rotated by a difference between atmospheric pressures applied to opposite sides of the second opening/closing plate; a drive unit connected to the first rotation shaft, the drive unit including a reversible motor configured to rotate the first rotation shaft in a forward direction or a reverse direction in response to an opening signal or a closing signal; a drive control unit connected to the first rotation shaft and the reversible motor and configured to control the reversible motor by cutting off the opening signal or the closing signal when the first rotation shaft is rotated by a predetermined angle; and a locking control unit connected to the first rotation shaft and the second rotation shaft and configured to lock the second rotation shaft to keep the second ventilation hole in a closed state when the first rotation shaft is rotated by a predetermined angle in response to the opening signal to open the first ventilation hole.
 2. The ventilation unit of claim 1, wherein the first ventilation hole includes a first lower ventilation hole and a first upper ventilation hole disposed in a vertical direction, the first rotation shaft including a first lower rotation shaft installed in the first lower ventilation hole and a first upper rotation shaft installed in the first upper ventilation hole, the first opening/closing plate including a first lower opening/closing plate provided in the first lower rotation shaft and a first upper opening/closing plate provided in the first upper rotation shaft.
 3. The ventilation unit of claim 2, wherein the first upper rotation shaft is connected to a first link, the first lower rotation shaft is connected to a second link, and the first link and the second link are interconnected by a connection link.
 4. The ventilation unit of claim 3, wherein the first link is an input link connected to a drive shaft of the reversible motor, and the second link is an output link.
 5. The ventilation unit of claim 3, wherein the locking control unit includes: a balancing blade formed in at least one end portion of the second rotation shaft and provided with a locking protrusion portion protruding in a horizontal direction; and a fixing blade connected to the connection link and configured to move upward, make contact with the locking protrusion portion and hold the balancing blade against movement when the first rotation shaft is rotated by a predetermined angle in response to the opening signal.
 6. The ventilation unit of claim 5, wherein the locking protrusion portion includes at least two locking protrusion portions spaced apart from each other in the horizontal direction, and when the first rotation shaft is rotated, the fixing blade is configured to move upward, make contact with the two locking protrusion portions and horizontally fix the balancing blade.
 7. The ventilation unit of claim 2, wherein the first frame includes a dividing frame configured to divide the first lower ventilation hole and the first upper ventilation hole.
 8. The ventilation unit of claim 7, wherein the dividing frame becomes gradually thinner toward one end portion thereof.
 9. The ventilation unit of claim 1, wherein stopper strips are formed in a central portion of an inner surface of the first frame and in a central portion of a dividing frame, and the first opening/closing plate is seated on the stopper strips when the first rotation shaft is rotated by a predetermined angle.
 10. The ventilation unit of claim 9, wherein protrusion portions are formed in a central portion of an inner surface of the second frame and in a central portion of a lower surface of the second frame, heater insertion grooves are provided in the stopper strips and the protrusion portions, and heaters are fitted to the heater insertion grooves to prevent ice formation in the first and second frames and the first and second opening/closing plates.
 11. The ventilation unit of claim 1, wherein the drive control unit includes: a first micro switch operatively connected to the first rotation shaft and configured to cut off the opening signal when the first rotation shaft is rotated by a predetermined angle in response to the opening signal; a second micro switch operatively connected to the first rotation shaft and configured to cut off the closing signal when the first rotation shaft is rotated by a predetermined angle in response to the closing signal; and a drive circuit including relays respectively connected to the first and second micro switches and configured to stop the reversible motor when one of the opening signal and the closing signal is cut off.
 12. The ventilation unit of claim 11, wherein the first ventilation hole includes a first lower ventilation hole and a first upper ventilation hole disposed in a vertical direction, the first rotation shaft including a first lower rotation shaft installed in the first lower ventilation hole and a first upper rotation shaft installed in the first upper ventilation hole, the first opening/closing plate including a first lower opening/closing plate provided in the first lower rotation shaft and a first upper opening/closing plate provided in the first upper rotation shaft.
 13. The ventilation unit of claim 12, wherein a first link connected to the first upper rotation shaft is configured to rotate by a predetermined angle in an opening direction with respect to the first upper rotation shaft and then to make contact with the first micro switch to cut off the opening signal, and a second link connected to the first lower rotation shaft is configured to rotate by a predetermined angle in a downward direction with respect to the second lower rotation shaft and then to make contact with the second micro switch to cut off the closing signal.
 14. The ventilation unit of claim 1, wherein the second opening/closing plate is configured to be opened when a difference is generated between atmospheric pressures applied to opposite sides of the second opening/closing plate and to be closed when the difference between atmospheric pressures is removed, the second rotation shaft is positioned in an uppermost area of the second ventilation hole, and the second opening/closing plate has a gravity center that is lower than the second rotation shaft so that the second opening/closing plate closes the second ventilation hole by an own weight of the second opening/closing plate.
 15. The ventilation unit of claim 14, wherein the second opening/closing plate has a recess region disposed in a lower portion thereof and depressed in a concave shape so as to receive an air pressure, and the second opening/closing plate has a lower end surface that makes contact with a lower horizontal frame, the lower surface formed into a curved surface so as to minimize a frictional resistance between the second opening/closing plate and the lower horizontal frame when opening and closing the second ventilation hole.
 16. The ventilation unit of claim 1, wherein the second opening/closing plate is configured to be opened by a difference between atmospheric pressures applied to front and rear sides of the second opening/closing plate and, when the difference between atmospheric pressures is removed, the second opening/closing plate is returned to a closed position by a restoring force of a return spring provided in one end portion of the second rotation shaft.
 17. The ventilation unit of claim 1, wherein the second opening/closing plate is configured to be opened by a difference between atmospheric pressures applied to front and rear sides of the second opening/closing plate, when the difference between atmospheric pressures is removed, the second opening/closing plate is returned to a closed position by a restoring force of a return spring provided in one end portion of the second rotation shaft, and when the second opening/closing plate comes close to the closed position, air tightness of the second opening/closing plate is enhanced by a magnetic force acting between a first magnetic portion provided in a lower end portion of the second opening/closing plate and a second magnetic portion provided in the second frame in a corresponding relationship with the first magnetic portion.
 18. The ventilation unit of claim 1, further comprising: a temperature controller configured to supply the opening signal and the closing signal to the reversible motor depending on a temperature of a storeroom in which the ventilation unit is installed.
 19. The ventilation unit of claim 1, further comprising: a ventilation fan disposed on one side surface of the first frame and configured to discharge or supply an air through the first ventilation hole.
 20. The ventilation unit of claim 19, wherein the ventilation fan is configured to operate when the opening signal is supplied and to stop when the closing signal is supplied.
 21. A preservation system, comprising: a first storeroom having a heat source; a second storeroom disposed adjacent to the first storeroom with a wall interposed between the first storeroom and the second storeroom, a first atmospheric pressure equilibrium ventilation unit installed in the wall and configured to supply an air existing within the first storeroom to the second storeroom; and a second atmospheric pressure equilibrium ventilation unit installed in the wall near the first atmospheric pressure equilibrium ventilation unit and configured to supply an air existing within the second storeroom to the first storeroom, wherein at least one of the first and the second atmospheric pressure equilibrium ventilation units include: a first frame assembly including a first frame configured to define a first ventilation hole, a first rotation shaft installed in the first ventilation hole, and a first opening/closing plate provided in the first rotation shaft and configured to rotate together with the first rotation shaft to open and close the first ventilation hole; a second frame assembly disposed adjacent to the first frame assembly, the second frame assembly including a second frame configured to define a second ventilation hole, a second rotation shaft installed in the second ventilation hole and a second opening/closing plate provided in the second rotation shaft and configured to rotate together with the second rotation shaft to open and close the second ventilation hole, the second opening/closing plate configured to open the second ventilation hole by being rotated by a difference between atmospheric pressures applied to opposite sides of the second opening/closing plate; a drive unit connected to the first rotation shaft, the drive unit including a reversible motor configured to rotate the first rotation shaft in a forward direction or a reverse direction in response to an opening signal or a closing signal; a drive control unit connected to the first rotation shaft and the reversible motor and configured to control the reversible motor by cutting off the opening signal or the closing signal when the first rotation shaft is rotated by a predetermined angle; and a locking control unit connected to the first rotation shaft and the second rotation shaft and configured to lock the second rotation shaft to keep the second ventilation hole in a closed state when the first rotation shaft is rotated by a predetermined angle in response to the opening signal to open the first ventilation hole.
 22. The system of claim 21, wherein the first storeroom is a low-temperature storeroom having a low-temperature heat source, the second storeroom is a heat-receiving low-temperature storeroom, which receives a cold air from the first storeroom, and the heat source of the first storeroom includes a freezer.
 23. The system of claim 21, wherein the first storeroom is a heat source warmer cabinet having a heat source, the second storeroom is a heat-receiving warmer cabinet, the heat source of the first storeroom includes a heater and a heat pump.
 24. The system of claim 21, further comprising: a temperature controller configured to supply the opening signal and the closing signal to the reversible motor depending on internal temperatures of the first and second storeroom.
 25. The system of claim 21, wherein at least one of the first and second atmospheric pressure equilibrium ventilation units further includes a ventilation fan disposed on one side surface of the first frame and configured to discharge or supply an air through the first ventilation hole.
 26. The system of claim 25, wherein the ventilation fan is configured to operate when the opening signal is supplied and to stop when the closing signal is supplied.
 27. The system of claim 21, wherein the first ventilation hole includes a first lower ventilation hole and a first upper ventilation hole disposed in a vertical direction, the first rotation shaft including a first lower rotation shaft installed in the first lower ventilation hole and a first upper rotation shaft installed in the first upper ventilation hole, the first opening/closing plate including a first lower opening/closing plate provided in the first lower rotation shaft and a first upper opening/closing plate provided in the first upper rotation shaft.
 28. The system of claim 27, wherein the first upper rotation shaft is connected to a first link, the first lower rotation shaft is connected to a second link, the first link and the second link are interconnected by a connection link, and when the first rotation shaft is rotated by a predetermined angle in response to the opening signal, a fixing blade provided in an upper end portion of an extension arm extending from the connection link is configured to push up a locking protrusion portion of a balancing blade formed in one end portion of the second rotation shaft and to hold the balancing blade against movement.
 29. The system of claim 21, wherein the drive control unit includes: a first micro switch operatively connected to the first rotation shaft and configured to cut off the opening signal when the first rotation shaft is rotated by a predetermined angle in response to the opening signal; a second micro switch operatively connected to the first rotation shaft and configured to cut off the closing signal when the first rotation shaft is rotated by a predetermined angle in response to the closing signal; and a drive circuit including relays respectively connected to the first and second micro switches and configured to stop the reversible motor when one of the opening signal and the closing signal is cut off.
 30. The system of claim 21, further comprising: an external atmospheric pressure equalizer installed in at least one of the first and second storerooms and configured to maintain pressure equilibrium between the inside and outside of the first and second storerooms.
 31. The system of claim 21, wherein the first storeroom includes a low-temperature heat source, and an atmospheric pressure valve is installed in the second storeroom having a relatively high temperature without installing an external atmospheric pressure equalizer in the first storeroom having a relatively low temperature, so that an external air having a high temperature enters the second storeroom having a relatively high temperature to adjust atmospheric pressures of the first and second storerooms, without directly infiltrating into the first storeroom having a relatively low temperature, thereby preventing a sudden temperature change and a thermal shock otherwise generated when a hot air is directly infiltrated into the first storeroom having a relatively low temperature.
 32. The system of claim 21, wherein the first storeroom includes a high-temperature heat source, and an atmospheric pressure valve is installed in the second storeroom having a relatively low temperature without installing an external atmospheric pressure equalizer in the first storeroom having a relatively high temperature, so that an external air having a low temperature enters the second storeroom having a relatively low temperature to adjust atmospheric pressures of the first and second storerooms, without directly infiltrating into the first storeroom having a relatively high temperature, thereby preventing a sudden temperature change and an energy loss otherwise generated when a cold air is directly infiltrated into the first storeroom having a relatively high temperature.
 33. The system of claim 21, wherein a gas existing within the storerooms is detected, and if the detected gas is a gas generated by fire, the gas existing within the storerooms is discharged to the outside while supplying an external fresh air into the storerooms.
 34. The system of claim 21, wherein a gas existing within the storerooms is detected, and if the detected gas is a toxic gas rather than a gas generated by fire, the gas existing within the storerooms is discharged to the outside while supplying a pre-prepared oxygen gas or a gas capable of neutralizing the toxic gas into the storerooms. 